The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A wireless power interface uses an inductively-coupled loop antenna to provide power for a device without a physical connection or contact with the device. The Alliance for Wireless Power (A4WP™) has developed a wireless power interface suitable for, among other things, charging a battery of a mobile device.
An A4WP interface transfers power from a transmitting antenna to a receiving antenna using a 6.78 MHz magnetic field. The transmitting antenna and the receiving antenna are tuned to resonate at 6.78 MHz. A voltage induced on the receiving antenna can be high, and may exceed the maximum voltages that can be handled by an integrated circuit technology used in a portable device such as a mobile phone or tablet.
Operation of the A4WP interface includes the generation of a wide range of voltages on outputs of the receiving antenna. Furthermore, a charging current delivered from the A4WP interface to a battery must be controlled to avoid damaging the battery.
Near Field Communication (NFC) is a standard for short-range wireless communication between two devices. An NFC communication uses inductively-coupled loop antennas to transfer information between devices using a 13.56 MHz magnetic field. The NFC antennas are tuned to resonate at 13.56 MHz. Voltages generated on the NFC antennas during NFC operations are generally low.
An antenna suitable for both A4WP power reception and for NFC communications is tuned to resonate at 6.78 MHz during an A4WP wireless charging operation and tuned to resonate at 13.56 MHz during an NFC operation. Components connected to the antenna are selected to withstand the voltages generated on the antenna during the A4WP wireless charging operation.